All three of these plants are associated with witchcraft. Bound together with human or animal fat, each was an essential ingredient in the magical flying ointment witches rubbed on their bodies before taking to the skies to attend their Sabbaths. All too have hallucinatory properties which would have aided the perception that this was actually happening. In particular, deadly nightshade can confer the sensation of spiraling into the sky or of metamorphosing into an animal, as well as producing powerful sexual hallucinations. This plant is sacred to witch-goddess Hecate and is said to be tended by the devil, while henbane is known colloquially as the “devil’s eye.” Dogwood, meanwhile, populates a haunted copse in Virgil’s Aeneid: when the hero Aeneas breaks off a branch to adorn an altar, it drips black blood.
You can find a selection of recipes for flying ointment here, though you are strongly advised not to brew up any of these toxic concoctions!